Microwaves are a form of electromagnetic radiation, characterized by frequency. Most microwave ovens operate at a frequency of 2,450 million cycles per second (2450 MHz). Energy is delivered in the form of an orthogonal wave, with electrical and magnetic components. Microwaves in a microwave oven are generated by means of a magnetron. The waves scatter in all directions inside the oven cavity to food placed in the cavity. The walls of a microwave are usually coated to reflect microwaves. Most ovens, in an attempt to distribute the waves evenly, have a fan which reflects the radiation randomly and a turn table which rotates the food.
In microwave ovens, food is placed on the turn table and heat is generated by the application of the microwaves to the ingredients of the food and sometimes even the packaging itself. The varying electric field of microwaves is responsible for most of the heating of food in microwave ovens, since the food does not interact with the magnetic field. The ions in the food and the water in the air of the microwave oven are accelerated by the electric field, thus giving kinetic energy to the ions, and converting that kinetic energy to heat. The higher the frequency range of the microwave oven increases the penetration depth of the microwaves into the food, and thus heating faster. Due to undesirable field distribution, microwaves hitting the sidewalls of a food container, and differences in penetration depth in different foods, it is not uncommon to see the center of a food item unacceptable colder than the outlying edges.
Consumers of frozen foods are often looking for convenience, value, and durability. Multiple food items in a microwavable entrée typically are limited to selections of food items that heat at similar rates to reach a singular temperature amongst all food items in the same amount of time.
However, some food products with multiple food items do not lend themselves to being heated at the same or similar rates. For example, pie à la mode contains a product meant to be served frozen and a food product meant to be served hot. Particularly, frozen desserts are not typically heated by microwave energy, as they are meant to be served at lower temperatures. There is a need to provide a solution where various types of food items that use the concept of undesirable field distribution, so that frozen food items can be kept in the frozen state while other food items are heated by microwave energy. The present invention is aimed at one or more of the problems identified above.